1. Field of the Invention.
This invention relates generally to a bipolar electrosurgical instrument, and more particularly to an electrosurgical instrument that incorporates bipolar electrodes at each clamp member such that electrocoaptation can be achieved.
2. Discussion of Related Art.
In surgery, removal of diseased tissue results in bleeding by the healthy tissue. Traditionally, this bleeding has been controlled by clamping the tissue to mechanically squeeze the bleeding tissue, cutting the affected area and ligating the clamped pedicle.
Recently, electrocoagulating instruments have been used to accomplish this same objective. These instruments include at least one conductive electrode through which radio frequency energy is conducted to either a remote conductive body-plate (monopolar) or to a second, closely spaced conductive electrode (bipolar). Current passing through the gap between the two electrodes coagulates blood and other body fluids placed therebetween.
Monopolar electrocautery instruments suffer from the fact that the return path between the active electrode and the large-area body-plate can be unpredictable as the electrical current seeks the return electrode through the path of least resistance. In bipolar electrosurgical instruments, the two electrodes are closely spaced to one another, usually at the distal of an instrument handle. The return path is very short and only involves the tissue and fluids in the space between the electrodes.
A problem encountered with both monopolar and bipolar electrocoagulation instruments is the failure to control completely the bleeding due to larger vessels. While the use of electricity for hemostasis is appropriate for capillaries and smaller vessels that are sealed by coagulation of the blood in the vessels, larger arteries and vessels need to be sealed by coaptation-the compression and fusion of the inner walls of the occluded artery.
For example, bipolar scissors have been developed with blades at the distal tip performing coagulation and cutting of the tissue with a mechanical shearing action. The two blades are insulated from one another, allowing them to function as bipolar electrodes for electrocoagulating small blood vessels in the surgical field. U.S. Pat. No. 5,352,222 discloses such a surgical scissor with bipolar features. While these instruments are utilized for coagulation of smaller vessels, it is impossible to approximate larger arteries and veins to achieve coaptation. A need thus exists for an instrument to crush larger arteries and veins to approximate and coaptate these tissues using RF energy.
Another concern with electrosurgical instruments is the lateral spread of current to adjacent tissue. Unregulated current flow damages this adjacent tissue, which is not intended to be coagulated or cauterized. Present-day, bi-polar electrosurgical forceps and clamps used in endoscopy do not exert sufficient force to crush tissues such as ligaments sufficiently to consistently compress and coaptate the arteries and veins therein. Thus, because the distance between these instruments' clamp surfaces and therefore the volume of the crushed tissue is determined by the thickness of the dense tissue captured therein, the current flow at the edge of the electrode arcs outwardly into the surrounding normal tissue at uneven and unpredictable rates. Thus a need exists for an instrument that distributes crushing force and creates a consistent final volume of the tissue captured between the clamping surfaces of the clamp.
A need therefore exists for a bipolar electrosurgical clamp to perform compression and controlled bipolar electrocoagulation and electrocoaptation of large arteries and veins.